The present invention relates to laser modules, and more particularly to a compact laser module which is simple in structure, easy to assemble, and practical in use.
Various laser modules have been designed for use in laser pointers, laser range finders, etc. FIGS. 1A and 1B show a prior art laser module which is generally comprised of a lens holder 1, a lens 2, a cylindrical casing 3, and a base 4. The lens 2 is mounted inside the stepped longitudinal through hole on the lens holder 1, with its convex surface disposed toward the front. The lens holder 1 has an outer thread 11 around the rear end thereof threaded into an inner thread 31 on the cylindrical casing 3. The base 4 is made of circular shape, having a LD (laser diode) chip 41 and a photo detector 42 at one side and a plurality of contact pins 43 at an opposite side. The base 4 is disposed inside the cylindrical casing 3. A protective cap 45 with a window glass 46 is covered on the base 4 over the LD chip 41 and the photo detector 42. The contact pins 43 of the base 4 are connected to a control circuit board 44. By means of turning the lens holder 1 relative to the cylindrical casing 3, the distance between the lens 2 and the LD chip 41 is adjusted. When adjusted, the connection between the lens holder 1 and the cylindrical shell 3 is sealed by a glue. The aforesaid laser module has drawbacks as outlined hereinafter.
i) The laser module is expensive to manufacture because it consists of a big number of component parts; PA1 ii) The laser module is complicated to assemble and repair because its structure is complicated; PA1 iii) The lens must fit in the stepped longitudinal through hole on the lens holder or it may displace, however, when fitting the lens into the lens holder the lens may be broken easily; PA1 iv) The lens and the protective cap 45 are difficult to process because of their small sizes; PA1 v) It is difficult to seal the protective cap to the base 4, and therefore the problem of high defective rate cannot be eliminated; PA1 vi) The lens holder may be turned relative to the cylindrical casing, causing the focus changed; and PA1 vii) When the laser beam from the LD chip passes through the lens, it may be partially refracted by the inside wall of the lens holder causing a halo to produce, and therefore the performance of the laser module is affected.